I. Field of the Invention
The invention relates to an apparatus for producing flexible stand-up pouches and, in particular, an apparatus for punching holes in a web during production of the pouch.
II. Description of the Prior Art
It is well known to produce flexible pouches from a continuous web of plastic film. The web is preprinted with the label and product information. A registration eyemark is formed along one edge of the web for each preprinted panel. The web is fed to a knife cutter. A sensor such as an electronic eve is used to detect the registration mark and generate a signal to stop the web and initiate the knife cutter to cut a panel from the web. Fitments are then attached to the panel and the pouch is formed by sealing the edges.
When a stand-up style pouch is being produced, a pair of holes are punched in the web in order to facilitate forming the welding of the base of the stand-up pouch. These holes permit welding of the corners of the leading and trailing edges of the pouch to the base to form gussets on the sides. The holes are punched in the web by a die cutter before the web moves to the knife cutter to form the panels. The die cutter is positioned upstream of the knife cutter and is activated to punch the holes when the web is stopped downstream at the cutting station.
However, the length between the registration marks on the web or pitch is not always equal due to shrinkage or stretch during the printing of the web. The length of each pitch or panel can vary as much as +/-0.0625 inches per pouch. The result of this variability in length can cause a variety of hole punching problems when the holes are punched upstream of the cutoff knife. As an example, if the stand-up hole punches are 20 pitches upstream of the cutoff knife and the variability of the web is +/-0.0625 inches, the hole punch could be theoretically +/-(20)*0.0625 inches or +/-1.25 inches off. The position of the hole punch must be manually adjusted whenever the web material has a length variation, a splice, or if there is a roll change. This results in a great slow down in the process.
Accordingly, it would be advantageous to automatically adjust the position of the die cutter to punch the holes in the proper position.